Both parts have emmision set only one shows it, though
It must have been a glitch with Cycles. The car is inside a warehouse environment, with two other cubes acting as doors to block all sunlight and slowly move to let sunlight in. I just had to hide the doors and unhide them, and it somehow reset the lighting. In the future if anyone comes across this, just change some stuff up in your scene that affect lighting, I guess. Someone else also said they had the same issue, and when they created a new Blender file it worked. If you don't have too much to lose, that is also an option.